1. Field of the Invention
The present invention relates to an image communicating apparatus, a control method therefor, and a storage medium storing a program.
2. Description of the Related Art
A method of using an IP network as a communication path for performing voice communication by IP (Internet Protocol) phones or image communication complying with T.38 of ITU-T recommendation has been established in recent years. In T.38, a G3 FAX (T.30) signal is converted into an IP message on the IP network, and transmitted in real time. Furthermore, deemed voice communication in which a modem signal tone is deemed as a voice to form PCM data and the PCM data is communicated as a voice packet on the IP network is performed. FAX communication using the T.38 protocol can decrease a bandwidth as compared with deemed voice communication requiring a voice bandwidth, and does not require modulation of data into a modem signal, thereby allowing high-speed communication.
On the other hand, in deemed voice communication, it is possible to communicate with a G3 FAX apparatus on a conventional analog telephone network connected via a VoIP GW (Voice over IP Gateway) arranged on the IP network. Furthermore, on the IP network, it is possible to simultaneously create one or a plurality of sessions, and parallelly execute a plurality of communication processes including, for example, voice communication and image communication. A private IP network can be used as a communication path, and an NGN (Next Generation Network) can be used as a communication path. The NGN is an IP network which includes a bandwidth guarantee function and security function in the network itself, and integrally implements a phone service, video communication service, data communication service, and the like. SIP (Session Initiation Protocol) in which a virtual session is established between communicating apparatuses on the IP network or NGN and a service is provided while the session is established has become widespread. Communicating apparatuses which have establish a session using SIP are provided with services of various forms which perform voice communication or image communication or simultaneously perform both of them using a protocol such as IP or VoIP (Voice Over IP).
There are provided various forms of image communicating apparatuses. For example, there is provided an image communicating apparatus which has an IP phone function and can connect a PSTN (Public Switched Telephone Network)-capable analog telephone as an external telephone. To control a PSTN-capable telephone, a SLIC (Subscriber Line Interface Circuit) for controlling a telephone is required. The SLIC has a function of performing D/A conversion or A/D conversion of a speech voice signal, a function of generating a calling signal to cause the ringer of a telephone to ring, a function of generating an off-hook voltage of the telephone, a function of detecting off-hook, and the like. The SLIC generates various tone signals after detecting off-hook, and detects a DTMF (Dual Tone Multi Frequency) signal or dial pulse signal sent by the telephone. Since such SLIC can provide a function of emulating a line, it can connect an analog telephone to the IP network without the intervention of the PSTN.
In the case of an incoming voice call, the medium type of a session establishment request (INVITE signal) by SIP is “audio” (voice). In the case of T.38, the medium type is “application” or “image”. Therefore, communication can be discriminated. With this feature, when an INVITE signal with a medium type “audio” is received from a calling side, the SLIC discriminates communication as voice communication to generate a calling signal, thereby causing the ringer of an analog telephone to ring. When the called-side user responds with the analog telephone, the SLIC detects the off-hook of the analog telephone to stop the calling signal, and transmits a successful response (200 OK) to the calling side. The calling side returns ACK to establish an audio session, thereby entering a voice communication state.
The SLIC for controlling a telephone is necessary between the IP network and a PSTN-capable telephone. Since it is generally desirable that the telephone is always available, it is necessary to always supply power to the SLIC for controlling a telephone. It is also necessary to always supply power to the main CPU of a controller circuit for controlling the SLIC so as to be operable.
On the other hand, the image communicating apparatus has an energy saving mode for reducing the power consumption, and the state of the energy saving mode will also be referred to as a sleep mode. To satisfy the standard by reducing the electric current consumption in the energy saving mode, it is necessary to cut off power supply to a portion such as a SLIC or main CPU for executing telephone control. If, however, this is done, the telephone cannot be used in the energy saving mode. A measure to cope with this is required.
Japanese Patent Laid-Open No. 10-164292 describes a technique in which after a facsimile apparatus enters a standby state with low power consumption, if an off-hook detection circuit detects the off-hook of a telephone, the facsimile apparatus is activated from the standby state with low power consumption. Furthermore, Japanese Patent Laid-Open No. 2006-295791 describes a technique of limiting the display and operation of an unusable function when setting which of a handset and a slave is to be used. Note that the handset is assumed to be a telephone without any operation function such as a calling ten-key pad for instructing a partner destination. The slave is assumed to be a telephone with an operation function such as a calling ten-key pad which can be used to instruct a partner destination.
Image communicating apparatuses which perform voice communication via an IP network include an image communicating apparatus capable of connecting, as an external telephone, a telephone which is connected to the PSTN and used. To connect a PSTN-capable telephone, a telephone control unit (SLIC) for controlling a telephone is necessary. As the telephone control unit, the above-described SLIC having a voice data conversion function, a calling signal control function, and the like is used. Since, however, the telephone is required to always operate for an incoming call, it is necessary to always supply power to the SLIC to be operable. Since the SLIC is controlled by the main CPU of the controller circuit, it is also necessary to always supply power to the main CPU to be operable. Consequently, it is impossible to sufficiently reduce the power consumption in the sleep mode.